Systems for separating a product contained as a solvent in a solution to be processed are known from the documents WPO 2007/147013 A1, J. R. McCutcheon, R. L. McGinnis, M. Elimelech: “A novel ammonia-carbon dioxide forward (direct) osmosis desalination process” (published in Desalination, Vol. 174, No. 1, 2005, pages 1 to 11), US 2006/0144789 A1 and WO 2007/146094 A2.